The Gene OntologyTM (GO) Consortium
(PDF) is developing
controlled vocabularies for describing gene products, applicable to all eukaryotes. The
SIFTS initiative
at the European Bioinformatics Institute
has mapped PDB IDs and corresponding chain IDs to GO terms. Please note that not all PDB IDs/chains have been mapped to GO terms.

Here you can browse the GO biological process hierarchy, view the number of associated PDB structures, and search for specific associated structures.